Tool Use to Modify Calls by Wild Orang-Utans

Peters, Helga H.

doi:10.1159/000049943

Cited by 17 publications

(16 citation statements)

References 6 publications

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“…This functional use is plausible because orang-utans are arboreal apes living in dense forests, where visibility is usually poor and rarely sufficient to make accurate visual assessments of body size, particularly in disturbing encounters when orang-utans use displays and missiles towards potential predators. This way, the visual salience hypothesis (Peters 2001) for the function of the kisssqueak forms also seems unlikely owing to poor visibility and because the dropping of leaves is not executed in isolation, but in combination with branch-shaking, breaking and throwing for example. Although one might argue that individuals of bigger body size classes (e.g.…”

Section: Resultsmentioning

confidence: 99%

“…However, tool-based innovations in acoustic communication that modify the acoustical properties of a call have been virtually absent, and the only case where such an innovation has been proposed concerns orang-utans (Van Schaik et al 2003, 2006Hardus et al 2009). Nevertheless, the function of this behaviour is not clear (Peters 2001), raising questions about its adaptiveness and dispersal within populations.…”

Section: Introductionmentioning

confidence: 99%

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Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?

et al. 2009

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Culture has long been assumed to be uniquely human but recent studies, in particular on great apes, have suggested that cultures also occur in non-human primates. The most apparent cultural behaviours in great apes involve tools in the subsistence context where they are clearly functional to obtain valued food. On the other hand, tool-use to modify acoustic communication has been reported only once and its function has not been investigated. Thus, the question whether this is an adaptive behaviour remains open, even though evidence indicates that it is socially transmitted (i.e. cultural). Here we report on wild orang-utans using tools to modulate the maximum frequency of one of their sounds, the kiss squeak, emitted in distress. In this variant, orang-utans strip leaves off a twig and hold them to their mouth while producing a kiss squeak. Using leaves as a tool lowers the frequency of the call compared to a kiss squeak without leaves or with only a hand to the mouth. If the lowering of the maximum frequency functions in orang-utans as it does in other animals, two predictions follow: (i) kiss squeak frequency is related to body size and (ii) the use of leaves will occur in situations of most acute danger. Supporting these predictions, kiss squeaks without tools decreased with body size and kiss squeaks with leaves were only emitted by highly distressed individuals. Moreover, we found indications that the calls were under volitional control. This finding is significant for at least two reasons. First, although few animal species are known to deceptively lower the maximum frequency of their calls to exaggerate their perceived size to the listener (e.g. vocal tract elongation in male deer) it has never been reported that animals may use tools to achieve this, or that they are primates. Second, it shows that the orang-utan culture extends into the communicative domain, thus challenging the traditional assumption that primate calling behaviour is overall purely emotional.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?

et al. 2009

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“…Recently, researchers have started to describe the way in which apes combine their signals; with gestures, vocalizations, and facial expressions, among other signals, employed in a single communicative system. These studies have highlighted the importance of considering communication holistically Liebal et al 2011;Wilke et al 2017), as well as blurring the boundary between signal categories (e.g., orang-utans' use of their hands to modify the acoustic properties of some vocalizations: Lameira et al 2013;Peters 2001).…”

Section: Introductionmentioning

confidence: 99%

Gesture Use in Communication between Mothers and Offspring in Wild Orang-Utans (Pongo pygmaeus wurmbii) from the Sabangau Peat-Swamp Forest, Borneo

et al. 2019

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Research on captive and wild great apes has established that they employ large repertoires of intentional gestural signals to achieve desired goals. However, gestural research has focused on African great apes, with orang-utan data limited to a few captive studies. We address this gap by describing gesture use in wild Southwest Bornean orang-utan (Pongo pygmaeus wurmbii) mother and offspring pairs. We conducted focal follows on 16 individuals in the Sabangau peatswamp forest in Borneo, Indonesia. The resulting 681 h of video footage yielded 1299 communicative signals: 858 vocal signals and 441 gestural signals. Eleven vocal signal types and 21 gesture types met the criteria for inclusion in the repertoire; however, the gestural repertoire did not approach asymptote and further gesture types will likely be identified in the future. Signalers used gestures of any modality in higher frequency when the recipient was paying visual attention, and took the recipient's visual attention into account when selecting gesture modalities. Orang-utans employed hands and arms more than legs and feet in gesturing, but were more flexible in their choice of limb than chimpanzees using the same gestures. Orang-utans were highly responsive to gestural requests, using them to achieve eight goals and, where successful, responding either before gesturing ended or in <1 s in 90% of communications. Our findings on the range of gesture types and impact of visual attention support findings from captive orang-utans; and those on responsiveness and limb use highlight the importance of studying ape communication in the social and ecological context to which it is adapted.

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“…Galdikas (1983) observed wild orangutans "snag-crashing," in which a large dead branch, or "snag," was pushed out of the tree and towards intruders. Peters (2001) noted that Gunung Palung orangutans throw fruit at humans, in addition to branch dropping.…”

Section: ) Weapons and Displaymentioning

confidence: 99%

“…Orangutans at Gunung Palung National Park in Borneo regularly use leaves as tools to modify their kiss-squeak vocalization during agonistic displays towards humans (Peters, 2001). First, the ape strips leaves from a branch, then holds the leaves to their mouth and performs their vocalization without crushing the leaves.…”

Section: ) Vocalization Modificationmentioning

confidence: 99%

Comprehension of tools by orangutans: Causality, tool properties, and manufacture

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Tool Use to Modify Calls by Wild Orang-Utans

Cited by 17 publications

References 6 publications

Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?

Tool use in wild orang-utans modifies sound production: a functionally deceptive innovation?

Gesture Use in Communication between Mothers and Offspring in Wild Orang-Utans (Pongo pygmaeus wurmbii) from the Sabangau Peat-Swamp Forest, Borneo

Comprehension of tools by orangutans: Causality, tool properties, and manufacture

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